Self-bleeding double action hydraulic cylinder

ABSTRACT

A self-bleeding hydraulic cylinder system is provided. The system includes a hydraulic cylinder with an inner wall and an outer wall. A cylinder port is located in a top region of the hydraulic cylinder. A line port is located in a bottom region of the hydraulic cylinder. A sleeve covers at least a portion of the outer wall of the hydraulic cylinder, and a channel is formed between the sleeve and the outer wall of the hydraulic cylinder. The channel extends from the cylinder port to the line port such that air within the hydraulic cylinder is pushed through the cylinder port and through the channel to the line port in response to actuation of the hydraulic cylinder.

FIELD OF THE INVENTION

This invention relates to hydraulic cylinder systems and in particularto hydraulic cylinders capable of purging air from the system throughnormal actuation of the cylinder piston.

BACKGROUND

In conventional hydraulic systems, proper operation depends on theability to purge all compressible compounds from the system. Air is anexample of a compressible compound that must be purged from a hydraulicsystem to ensure proper operation. The entrapment of air in the systemor the dissolving of gas into hydraulic fluid may be problematic.Pressure drops, cavitation, reduced functionality, or general harm tothe system may occur due to the presence of entrapped or dissolved air.As a result, air must be purged from hydraulic systems to ensure properoperation.

Current approaches rely on the positioning of system components, the useof a vacuum, or continuous operation to purge air from the system. Oneapproach purges all air from the system through the creation a vacuum.Only once a sufficient vacuum is achieved is hydraulic fluid then addedto the system. However, this approach requires specialized equipment forthe creation of a vacuum. Another approach simply operates the hydraulicsystem for a period of time whereby the fluid moving through the systemwill push the air to a place in the system where it can then be purged.However, these approaches may not be feasible where the hydrauliccylinder is positioned near a high point of the hydraulic system.

Hydraulic cylinders may purge air from the system by placing hydrauliclines on top of the hydraulic cylinder. This allows the cylinder to pushair that has risen to the top of the system through the ports before thehydraulic fluid. Thus, any air entrapped in the system will enter thehydraulic lines first and be pushed to a point where it can then bepurged.

However, space constraints may prevent the positioning of hydrauliclines at the top of the system. As a result, the hydraulic ports andlines may need to be located on the bottom of the hydraulic cylinder. Inthis case, actuating the cylinder will push hydraulic fluid through theports and lines before the air that has risen to the top of the system.As a result, air may not be sufficiently purged from the system. Becausefluid was pushed through the hydraulic ports before the air, the air mayremain in the hydraulic lines and return to the cylinder when thecylinder is actuated in the opposite direction. Alternatively, air mayalso become dissolved into the hydraulic fluid in systems where fluid ispushed from the hydraulic cylinder before air. Thus, there exists a needfor a hydraulic cylinder having ports and hydraulic lines located on thebottom of the hydraulic cylinder that is also capable of purging airfrom the system through normal actuation of the cylinder.

SUMMARY

A self-bleeding hydraulic cylinder system is provided. The systemincludes a hydraulic cylinder with an inner wall and an outer wall. Acylinder port is located in a top region of the hydraulic cylinder. Aline port is located in a bottom region of the hydraulic cylinder. Asleeve covers at least a portion of the outer wall of the hydrauliccylinder, and a channel is formed between the sleeve and the outer wallof the hydraulic cylinder. The channel extends from the cylinder port tothe line port such that air within the hydraulic cylinder is pushedthrough the cylinder port and through the channel to the line port inresponse to actuation of the hydraulic cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an example self-bleeding hydrauliccylinder system.

FIG. 2 is a cross-sectional side view of an example self-bleedinghydraulic cylinder system installed in a housing and connected to a pumpand motor.

FIG. 3 is a close-up cross-sectional view of an alternative examplecylinder and sleeve configuration.

FIG. 4 is a close-up cross-sectional view of another alternative examplecylinder and sleeve configuration.

DETAILED DESCRIPTION

A self-bleeding, double-action hydraulic cylinder system is describedherein. In particular, the hydraulic cylinder system purges air from thecylinder through normal actuation of a cylinder piston.

As shown herein, a self-bleeding hydraulic cylinder system has ahydraulic cylinder with a cylinder port located in the top region of thehydraulic cylinder. A sleeve that functions as a manifold is used tocover the cylinder port. A line port is located in a bottom region ofthe hydraulic cylinder system, and a channel is formed between thehydraulic cylinder and the sleeve. The channel, for example, may be agroove formed in an outer wall of the cylinder, or alternatively formedin an interior wall of the sleeve. Upon actuation of the hydrauliccylinder, air may be pushed through the cylinder port and through thechannel to the line port. A hydraulic line leading to a pump and motormay also be connected to the line port of the sleeve. The hydrauliccylinder system may be mounted in a housing above pump or motor devicesand beneath a top wall of the housing.

Referring to FIG. 1, a cross-section of a hydraulic cylinder system 10is shown. Hydraulic cylinder system 10 is divided into a top region 12and a bottom region 14 and includes hydraulic cylinder 16 and sleeve 18.Top region 12 includes sites on the top half of the hydraulic cylinder16. Bottom region 14 includes sites on the bottom half of hydrauliccylinder 16.

Hydraulic cylinder 16 may be any type of hydraulic cylinder known tothose skilled in the art and may include a piston 17 to move hydraulicfluid and air within the cylinder. Hydraulic cylinder 16 also includescylinder port 20 located in top region 12 of hydraulic cylinder system10. In one embodiment, cylinder port 20 is located proximate to the topof hydraulic cylinder 16 and is formed from inner wall 22 to outer wall24 of the hydraulic cylinder.

Sleeve 18 functions as a manifold, providing a space through which airand hydraulic fluid may pass. Additionally, sleeve 18 may be made fromthe same material as outer wall 24 of hydraulic cylinder 16 or any othersuitable material. In an embodiment, sleeve 18 may be made of metal andwelded to hydraulic cylinder 16. Sleeve 18 includes line port 26 locatedin bottom region 14 of hydraulic cylinder system 10. In one embodiment,line port 26 may be located proximate to the bottom of hydrauliccylinder 16 and is formed from exterior wall 28 to interior wall 30 ofsleeve 18.

Channel 32 is formed when sleeve 18 encloses cylinder port 20 ofhydraulic cylinder 16. Channel 32 also extends from cylinder port 20 toline port 26. When hydraulic cylinder 16 is actuated, sleeve 18functions as a manifold allowing air and fluid to pass through cylinderport 20 and channel 32 to line port 26 as illustrated by arrows 25. Inone embodiment, channel 32 may be a groove 34 formed in outer wall 24 ofhydraulic cylinder 16, as seen in FIG. 2. In another embodiment, channel32 may be comprised of groove 34 formed in interior wall 30 of sleeve18, as seen in FIG. 3. In yet another embodiment, channel 32 may becomprised of groove 34 formed in both outer wall 24 of hydrauliccylinder 16 and interior wall 30 of sleeve 18, as seen in FIG. 4.

As seen in FIG. 1, groove 34 extends along the circumference of at leastone of side 36 of hydraulic cylinder 16. In particular, in theembodiment of FIG. 1, groove 34 is shown extending along thecircumference of both sides 36 of hydraulic cylinder 16. Groove 34 mayalso be milled into outer wall 24 of hydraulic cylinder 16 or may beformed in interior wall 30 of sleeve 18.

When hydraulic cylinder system 10 is in use, hydraulic line 38 may beattached to line port 26. Line port 26 may be formed in any manner knownto those skilled in the art to allow the attachment of hydraulic line38. When hydraulic cylinder 16 is actuated (during piston movement, forexample), air and fluid flowing through channel 32 to line port 26 willexit the channel through the line port and enter hydraulic line 38 asillustrated by arrows 25.

Referring now to FIG. 2, a hydraulic cylinder system 10 is shownpositioned in a housing 40 above a pump 42, vented reservoir 43, andmotor 44 to which the hydraulic cylinder system is attached. As seen inFIG. 2, example hydraulic cylinder system 10 includes cylinder ports 20and line ports 26 at each end of hydraulic cylinder 16. Examplehydraulic cylinder 16 contains hydraulic fluid 46 and air 48, which hasrisen to the top of the hydraulic cylinder.

Hydraulic cylinder system 10 also includes sleeves 18 attached to eachend of hydraulic cylinder 16 covering cylinder ports 20. Hydraulic lines38 are attached to example hydraulic cylinder system 10 and lead to pump42. Pump 42 is connected to vented reservoir 43 and motor 44. Pump 42and motor 44 may be any pump and motor known to those skilled in the artto be suitable for use in a hydraulic system. Vented reservoir 43 is afluid reservoir that is vented to the atmosphere.

Vented reservoir 43 may be used to account for the volumetricdifferences between either sides of hydraulic cylinder 16. Piston 17includes piston head 45 and piston shaft 47. Head 45 divides the chamberof hydraulic cylinder 16 into two sides, one side including shaft 47.The side of hydraulic cylinder 16 lacking shaft 17 may hold a greatervolume of fluid than the side that includes the shaft. Vented reservoir43 may be used to contain excess fluid 46 as the side of hydrauliccylinder 16 that includes shaft 47 is filled to capacity.

Vented reservoir 43 is also used as the bleed site for any air presentin the system. Because cylinder ports 20 are located in top region 12 ofhydraulic cylinder system 10, air 48 will be pushed through cylinderports 20 before hydraulic fluid 46. By pushing air 48 from hydrauliccylinder 16 before hydraulic fluid 46, the air ultimately be pushed toreservoir 43 at which point it will be purged from the system to theatmosphere.

As seen in FIG. 2, motor 44 powers pump 42, which pushes hydraulic fluid46 through one of hydraulic lines 38. Hydraulic fluid 46 exits one ofhydraulic lines 38 into corresponding channel 32 where it then travelsto corresponding cylinder port 20 and enters hydraulic cylinder 16actuating piston 17. As hydraulic cylinder 16 is actuated, air 48 ispushed through opposite cylinder port 20 followed by hydraulic fluid 46.Air 48 leads hydraulic fluid 46 through corresponding channel 32 tocorresponding line port 26 and into corresponding hydraulic line 38. Air48 then leads fluid 46 through pump 42 to vented reservoir 43. Air 48may then bubble through any fluid 46 present in vented reservoir 43escaping to the atmosphere.

Also shown in FIG. 2, hydraulic cylinder system 10 in this example maybe positioned at or just below top wall 50 of housing 40. Top wall 50may be an upper barrier of housing 40, or top wall 50 may be anothercomponent also installed in housing 40. In other embodiments, top wall50 may be other walls or barriers of housing 40. As seen in the examplein FIG. 2, adequate space to allow for the attachment of hydraulic linesto the top of the hydraulic cylinder is not achieved because hydrauliccylinder 16 is placed at a high point within housing 40 adjacent to topwall 50. Sleeve 18 functions as a manifold creating channel 32 betweenouter wall 24 of hydraulic cylinder 16 and interior wall 30 of thesleeve. This allows hydraulic lines 38 to be attached to the bottom ofhydraulic cylinder 16 while still positioning cylinder ports 20 at thetop of the hydraulic cylinder.

By way of example, the hydraulic cylinder system described herein may beinstalled in the housing of a vehicle door system. In an example vehicledoor system, the hydraulic cylinder system may need to be positionedabove the pump and motor and just below the top wall of the housingleaving little room for top-mounted hydraulic lines. In this examplesystem, because the hydraulic cylinder is positioned at the highestpoint of the system, air may rise to the top of the cylinder. Thehydraulic cylinder system described herein allows the installation of ahydraulic cylinder below the top wall of the housing and above the pumpand motor with bottom-mounted hydraulic lines. The sleeve encloses thetop-positioned cylinder ports and forms a channel to thebottom-positioned line ports. This allows air to be pushed from thehydraulic cylinder before the hydraulic fluid to a point at which it canbe purged. Thus, air may be bled from the hydraulic cylinder systemthrough normal actuation of the hydraulic cylinder without the need forspecial equipment or processes.

The invention illustratively disclosed herein suitably may be practicedin the absence of any element, part, step, component, or ingredientwhich is not specifically disclosed herein.

While in the foregoing detailed description this invention has beendescribed in relation to certain preferred embodiments thereof, and manydetails have been set forth for purposes of illustration, it will beapparent to those skilled in the art that the invention is susceptibleto additional embodiments and that a certain of the details describedherein can be varied considerably without departing from the basicprinciples of the invention.

1. A self-bleeding hydraulic cylinder system comprising: a hydrauliccylinder having an inner wall and an outer wall; a cylinder port locatedin a top region of the hydraulic cylinder; a line port located in abottom region of the hydraulic cylinder; a sleeve covering at least aportion of the outer wall of the hydraulic cylinder; and a channelformed between the sleeve and the outer wall of the hydraulic cylinder,the channel extending from the cylinder port to the line port such thatair within the hydraulic cylinder is pushed through the cylinder portand the channel to the line port in response to actuation of thehydraulic cylinder.
 2. The self-bleeding hydraulic cylinder system ofclaim 1 wherein the channel comprises a groove formed at the outer wallof the hydraulic cylinder.
 3. The self-bleeding hydraulic cylindersystem of claim 2 wherein the groove is milled in the outer wall of thehydraulic cylinder.
 4. The self-bleeding hydraulic cylinder system ofclaim 1 wherein the channel comprises a groove formed at an interiorwall of the sleeve.
 5. The self-bleeding hydraulic cylinder of claim 1wherein the channel comprises a groove formed at least one of: (a) theouter wall of the hydraulic cylinder; and (b) an interior wall of thesleeve.
 6. The self-bleeding hydraulic cylinder system of claim 5wherein the groove extends between the cylinder port and the line portalong a circumference of at least one side of the hydraulic cylinder. 7.The self-bleeding hydraulic cylinder system of claim 5 wherein thegroove extends along the circumference of both sides of the hydrauliccylinder between the cylinder port and the line port.
 8. Theself-bleeding hydraulic cylinder system of claim 1 wherein the cylinderport provides an opening extending from the inner wall of the hydrauliccylinder to the outer wall of the hydraulic cylinder.
 9. Theself-bleeding hydraulic cylinder system of claim 1 wherein the line portprovides an opening extending from an inner wall of the sleeve to anouter wall of the sleeve.
 10. The self-bleeding hydraulic cylindersystem of claim 9 wherein the line port is positioned proximate to abottom end of the channel.
 11. The self-bleeding hydraulic cylindersystem of claim 10 further comprising at least one hydraulic linecoupled with the line port, the at least one hydraulic line incommunication with a pump of the self-bleeding hydraulic cylindersystem.
 12. The self-bleeding hydraulic cylinder system of claim 10wherein the hydraulic cylinder is positioned above a pump or motor ofthe self-bleeding hydraulic cylinder system.
 13. The self-bleedinghydraulic cylinder system of claim 10 wherein the hydraulic cylinder isconfined within a housing and wherein the hydraulic cylinder ispositioned adjacent to a wall of the housing.
 14. The self-bleedinghydraulic cylinder system of claim 10 wherein the hydraulic cylinder iscontained within a housing of a vehicle door system and wherein the topof the hydraulic cylinder is positioned adjacent to a wall of thehousing.
 15. The self-bleeding hydraulic cylinder system of claim 10wherein the sleeve is welded to at least one end of the hydrauliccylinder.
 16. The self-bleeding hydraulic cylinder system of claim 1wherein the sleeve completely encloses at least one end of the hydrauliccylinder about the circumference of the at least one end of thehydraulic cylinder.
 17. The self-bleeding hydraulic cylinder system ofclaim 16 wherein a pair of sleeves are respectively positioned at eachend of the hydraulic cylinder.